This application claims the benefit of German application serial no. 19850737.2 filed Nov. 4, 1998 and German application serial no. 19901262.8 filed Jan. 15, 1999, which are hereby incorporated herein by reference, and which claims the benefit under 35 U.S.C. xc2xa7365 of International Application PCT/EP99/08401, filed Nov. 3, 1999, which was published in accordance with PCT Article 21(2) on May 11, 2000 in German.
The invention relates to an electromechanical component, particularly a component according to the preamble of claim 1.
In the electrotechnical industry, use is made for numerous applications of printed circuit boards which, firstly, serve the purpose of holding electronic components mechanically and, secondly, simultaneously produce electric connections between these components. Conventional printed circuit boards are frequently produced from hot-cured materials such as, for example, anionic resin paper or epoxy resin reinforced with glass fibres. These materials are combustible per se, and this is not acceptable for safety reasons. Consequently, these materials have flame-retardant chemicals added to them such as, for example, bromine compounds or organic phosphorous compounds which, in co-operation with other inorganic substances such as, for example, antimontrioxide as synergist, avoid the flammability of conventional printed circuit boards.
The flame-retardant additives in the printed circuit boards give rise, however, to substantial difficulties in the recycling of the printed circuit boards. In particular, the hot-curable materials cannot be recycled and must therefore finally disposed of in refuse dumps. Furthermore, it is possible to burn these materials, in which case substantial efforts are required in order to avoid toxic emissions which stem from the flame-retardant chemicals. For these reasons, there are relatively high costs for the removal at the end of the service life of a product which contains conventional printed circuit boards. With regard to the general trend towards a sustained economic approach, it is therefore desirable to provide components for electrotechnical applications which can be recovered with an acceptable economic outlay at the end of the service life of a product.
DE 24 13 158 A describes a punchable and drillable flame-retardant insulating plate for electrotechnical aims, which is produced from inorganic fibrous material, inorganic binder and inorganic filler as well as a heat-curable resin. The inorganic materials are not combustible whereas the organic resin is combustible. This insulating plate is a multi-component system.
Starting from here, it is the object of the invention to create a component for electrotechnical applications which avoid the disadvantages described at the beginning.
According to the invention, this object is achieved by means of a component according to claim 1. The component has a support layer, at least the top side of the support layer being covered by a covering layer. Both the covering layer and the support layer are produced from a relatively non-combustible plastic material. The covering layer and the support layer are permanently connected to one another and lend the component mechanical stability which suffices for the respective application. Furthermore, the covering layer bears electrically conducting material by means of whichxe2x80x94after a further structuring process, if appropriatexe2x80x94it is possible to produce electrical connections between electronic components.
The particular advantage of this component resides in the fact that the flame-retardant properties are achieved without additives which show up difficulties in recycling at the end of the service life of a product.
According to an exemplary embodiment of the invention, the covering layer can be constructed in a multilayer fashion from a plurality of layered films. This design is particularly advantageous wherever two or more of these films bear a conductor track structure, each plane of a conductor track structure being separated spatially from an adjacent plane by an electrically insulating film. If required, electric connections can also be produced between the planes.
In accordance with a first exemplary embodiment of the invention, the electrically conducting material is formed as a layer which completely covers the covering layer. This layer can, for example, consist of a thin layer of copper which is structured in conductor tracks using an etching technique. As an alternative thereto, the conductor tracks can also be produced using a hot embossing process or a selective chemical electroplating process.
However, it is also possible for the conductor tracks to be produced from a free-flowing material using a printing process, in particular a screen printing technique.
It is particularly advantageous when the covering layer is produced from LCP plastic material (Liquid Crystal Plastic) or polyetherimide (PEI). These materials are intrinsically flame-retardant and easy to recycle.
The support layer can expediently be produced from foamed plastic material. This has the advantage that the component is lighter as a whole, adequate mechanical stability simultaneously being achieved. Moreover, the foaming of the plastic leads to a saving in material, and so the costs for the component are comparable to the costs of a part which is produced from conventional material. However, it is also possible to produce the support layer from silicone, which permits a particularly cost effective application.
It is particularly advantageous when the covering layer is of flexible design such that the component can be deformed, for example when being mounted in an electrical device. The mechanical stability required of electric components during mounting can be achieved by virtue of the fact that the flexible covering layer is reinforced with a support layer in the regions specified for holding components, while the rigid support layer is lacking in the regions which are to remain flexible.
According to an exemplary embodiment of the invention, the component can be of flat design in the form of a printed circuit board. However, it is also possible for the component to have a three dimensional structure and be provided with mechanical functional elements. These mechanical functional elements can serve the purpose, for example, of holding heavy electronic components such as, for example, capacitors or transformers on the component without the need for additional fastening elements. Furthermore, the component can be designed such that it fulfils at least partly the purpose of an insulating housing for an electric device.
A further object of the invention is to specify a method in accordance with which the component according to the invention can be produced in a particularly favourable way.
This object is achieved by a method according to claim 18.